Key crop rotation is where you select three or four key crops that
take up the biggest area in your vegetable garden and rotate them.
All other vegetable crops are planted in the spaces not covered by
your key crops.

An example of key crop rotation. Corn in the front raised vegetable
bed, onions in the middle bed and tomatoes in the far bed along with
some sunflowers. The corn, onions and tomatoes are key crops while
the sunflowers are one of the other vegetables that I plant in
spaces left after the key crops have been planted.

Key crop rotation has it's disadvantages. Sometimes vegetables
from the same vegetable group are planted consecutively the same bed,
though this is fairly rare. It also means that the planting of leafy
greens, fruits, roots and then legumes in a sequential order is not
strictly followed. However the big advantage of key crop rotation is
that it is more flexible and a lot simpler to administer. You
don't tie yourself in knots trying to keep the various crop groups
separated.

The key crops are not fixed, it all depends on what vegetables you grow
that take up the most space. Nor do they all have to come from
different vegetable groups, though that is preferable.

My four key crops are tomatoes, corn, onions & carrots and broad beans &
peas. I rotate these four groups of vegetables across five beds of
varying sizes, planting all my other vegetable varieties that I grow in
whatever space is left after the key crops have been planted.

But whatever crop rotation you are practicing don’t forget to record
what was planted where in each season. If you do that you will find it
much easier to follow your particular plan.